Shape-assisted self-assembly

Self-assembly and molecular recognition are critical processes both in life and material sciences. They usually depend on strong, directional non-covalent interactions to gain specificity and to make long-range organization possible. Most supramolecular constructs are also at least partially governed by topography, whose role is hard to disentangle. This makes it nearly impossible to discern the potential of shape and motion in the creation of complexity. Here, we demonstrate that long-range order in supramolecular constructs can be assisted by the topography of the individual units even in the absence of highly directional interactions. Molecular units of remarkable simplicity self-assemble in solution to give single-molecule thin two-dimensional supramolecular polymers of defined boundaries. This dramatic example spotlights the critical function that topography can have in molecular assembly and paves the path to rationally designed systems of increasing sophistication.


Supplementary Figures
Supplementary Figure 1a. Examples of previous works on self-assembled 2D sheets from small molecules covering a range of different interactions and dimensions S1,S2 in addition to the work reported herein. Figure 1b. Examples of previous works on self-assembled 2D sheets from small molecules covering a range of different interactions and dimensions S3,S4 in addition to the work reported herein. Figure 1c. Examples of previous works on self-assembled 2D sheets from small molecules covering a range of different interactions and dimensions S5,S6 in addition to the work reported herein. Figure 1d. Examples of previous works on self-assembled 2D sheets from small molecules covering a range of different interactions and dimensions S7 in addition to the work reported herein.
Analytical data were in agreement with those reported in literature S13 .
Analytical data were in agreement with those reported in literature S13 .
Analytical data were in agreement with those reported in literature S14 .

2H-Car-H
Two different synthetic methods are herein reported for the synthesis of 2H-Car-H, the first one being a macrocyclization from carbazole 18, analogous to the rest of derivatives, and the second one based on a reverse Friedel-Crafts alkylation reaction on 2H-Car-tBu.
Analytical data match that of the previous macrocyclic synthesis.

Methods
All models were built using GaussView 6 and the corresponding optimizations carried out using Gaussian 16 revision C.01 S15 . For DFT calculations, the choice of functional was based on various examples from the literature. To avoid functional-specific errors, we decided to carry out the calculations using three different functionals: wB97XD S16 , PBE0 S17 and B3LYP S18 . All three functionals cover fairly distinct approximations and include explicitly or not effects such as longrange and dispersion corrections. As such and considering our results were consistent thorough, we are confident about the presented results. In all cases, the absence of imaginary frequencies (for ground-state calculations) or the presence of a unique imaginary frequency (for transition state calculations) was confirmed. In all cases, a conservative 6-31G(d,p) was used. The main reason for using this basis set is the relatively high number of atoms on the supramolecular tetramer calculations (232). Semi-empirical calculations use the PM6 method S19 as implemented in Gaussian.
The calculation of the stacks formed by 2H-Car-H using the B3LYP functional without dispersion correction resulted in the disassembly of the stack. When using the D3 dispersion correction by Grimme S20 , an equivalent structure to the other functionals was obtained with a comparable energy difference. Such behavior is expected considering the critical role of dispersion in these systems. The activation energy barrier for the isomerization of the carpyridine core was calculated on the 2H-Car-H structure. A redundant coordinate scan was performed by stepwise changing the dihedral angle of the carbazole-pyridine bond. The scan gave increasing and unhindered energy changes (Supplementary Table 5) until the most stable conformation became another local minimum (Supplementary Figure 56). Based on this scan, the corresponding transition state was calculated starting from a few of the high energy conformations using the Berny approximation. The transition state conformation could be found in this way. To estimate the energy barrier, the energies from the thermochemistry calculation (including Gibbs free energy correcting) where used for both the ground and the transition states. To confirm that the isomerization of the carpyridine core is a stepwise isomerization of the pyridine units and not a concerted flip, a 2D scan involving both pyridine units was carried out: A concerted flipping would require significantly more energy and, thus, we report here the energy of the transition to an intermediate conformation as the activation energy for the isomerization of the carpyridine core. Supplementary Figure 60. Optimized structure of a stack of six 2H-Car-C6 using the semiempirical PM6 method. Top, Top view. Bottom, Side views of the optimized stack. Slipped stacks did not yield stable solutions and resulted in collapsed or separated ensembles.

Definition of terms.
Function minimized: Σw(Fo 2 -Fc 2 ) 2 where w = [σ 2 (Fo 2 ) + (aP) 2 + bP] -1 and P = (Fo 2 + 2Fc 2 )/3 Fo 2 = S(C -RB) / Lp and σ 2 (Fo 2 ) = S 2 (C + R 2 B) / Lp 2 S = Scan rate C = Total integrated peak count R = Ratio of scan time to background counting time B = Total background count Lp = Lorentz-polarization factor R-factors: Rint = Σ|<Fo 2 > -Fo 2 | / ΣFo 2 summed only over reflections for which more than one symmetry equivalent was measured. Crystal-Structure Determination. -A crystal of C58H68N4, obtained from toluene and MeOH, was mounted on a cryo-loop and used for a low-temperature X-ray structure determination. All measurements were made on a Rigaku Oxford Diffraction XtaLAB Synergy diffractometer (1) with a Pilatus 200K hybrid pixel area detector using Cu Kα radiation (λ = 1.54184 Å) from a PhotonJet micro-focus X-ray source and an Oxford Cryosystems Cryostream 800 cooler. The unit cell constants and an orientation matrix for data collection were obtained from a least-squares refinement of the setting angles of 27011 reflections in the range 5° < 2θ < 157°. A total of 3658 frames were collected using ω scans with κ offsets, 4.8-19.0 seconds exposure time and a rotation angle of 0.5° per frame, and a crystal-detector distance of 40.0 mm. Data reduction was performed with CrysAlisPro S21 . The intensities were corrected for Lorentz and polarization effects, and a numerical absorption correction S22 was applied. The space group was uniquely determined by the systematic absences. Equivalent reflections were merged. The data collection and refinement parameters are given in Supplementary Table 7. A view of the molecule is shown in Supplementary Figure 61. The structure was solved by dual space methods using SHELXT-2018 S23 , which revealed the positions of all non-hydrogen atoms. Two XX groups are disordered over two conformations. Two sets of positions were defined for the atoms of each disordered XX group and the site occupation factors of the major conformations of these groups refined to 0.647(7) and 0.789(6), respectively. Two sets of positions were defined for the atoms of the XX group and the site occupation factor of the major conformation of the group refined to 0.572(4). Similarity restraints were applied to the chemically equivalent bond lengths and angles involving all disordered C-atoms, as well as to Supplementary Figure 61. X-ray structure of a crystal of 2H-Car-C6 grown from slow diffusion of methanol into toluene. Side chains and hydrogens are omitted for clarity. Blue colored molecules represent the repeating unit of packing along the crystal, with 3 carpyridines stacked and slipped on each other. The direction of the principal axis of curvature is retained across all carpyridines. The crystal was of very poor quality with high R-factor due to heavily disordered side chains. Note: There are three symmetry-independent molecules in the asymmetric unit. Although the basic structure, connectivity and conformation of the core of the molecules is visible, they should be considered very approximate. The R-factors remain high and other quality indicators indicate very low precision and accuracy. The standard uncertainties on bond lengths between core atoms is in the range 0.008-0.012 Å. The main factors leading to these issues are overall poor crystal quality, strong streaks of diffuse scattering (a consequence of disorder), which mean that the integrated intensities are very inaccurate, and severe disorder of the hexyl sidechains, which is difficult to model adequately. Attempts to model some of the side-chain disorder were unsuccessful, because it is apparent that there might not be just two conformations of a disordered hexyl group, but multiple positions for the atoms; or this appearance might also be related to the inaccurate

Side view
intensities. Therefore, just the average positions for the atoms of some of the side chains were used. Consequently, the model has are a few chemically unreasonable short contacts between molecules, so the conformations of the side chains should be understood to be very approximate. Similarity restraints applied to the anisotropic displacement parameters of all neighboring Catoms. Within the hexyl sidechains, all C-C bonds and 1,3 distances were restrained to be similar.